/Engine/Source/Editor/UnrealEd/Public/EditorActorFolders.h
Notify that a root object has been removed. Cleanup of existing folders with with root object.
void OnFolderRootObjectRemoved ( [UWorld](API\Runtime\Engine\Engine\UWorld) & InWorld, const [FFolder::FRootObject](API\Runtime\Engine\FFolder\FRootObject) & InFolderRootObject )